FDA notified healthcare professionals of reports of death and life-threatening adverse events such as respiratory depression and cardiac arrhythmias in patients receiving methadone. These adverse events are the possible result of unintentional methadone overdoses, drug interactions, and methadone's cardiac toxicities (QT prolongation and Torsades de Pointes).

The reports underscore the importance of knowing methadone's toxicities and unique pharmacologic properties, including dosing and monitoring recommendations.